Abstract: Sliding polymer-polymer surface contacts, due to their inherent elastic properties, exhibit
detachment waves also termed as Schallamach waves. Such waves effect the initiation and
propagation of wear along the sliding contacts. This paper presents quasi steady-state analysis of
such a sliding contact using finite element. The contact is modeled and nodal solutions for pressure
are obtained for small sliding steps. Analysis of orthogonal pressure components at the contact
nodes reveals the formation of Schallamach wave phenomenon. Further, appropriate wear law is
used for calculation of wear at nodal level.
Abstract: Considering the aerospace structures, the advantages of Al-Li alloys in comparison with
conventional aluminium alloys comprise relatively low densities, high elastic modulus, excellent
fatigue and toughness properties, and superior fatigue crack growth resistance. Unfortunately, these
alloys have some disadvantages due to highly anisotropic mechanical properties and due to a very
high crack growth rate for microstructurally short cracks. This could mean relatively early cracking
in high stress regions such as rivet holes in helicopter fuselage panels. Consequently a more
accurate approach in fatigue life analysis is requested. Considering that the 8090 T81 aluminium
alloy has been widely used in an helicopter structure, in particular in the bolted connection between
the stringers and the modular joint frame in the rear of the fuselage, it is extremely important to
found a reliable procedure for the fatigue life assessment of the component. Thus, using the results
of experimental tests made on panel specimens, a FE general model and two submodels of the
critical zone (involved in fatigue damage during the tests) have been modelled in order to
investigate the complex state of stress near the rivets holes. These stress values obtained have been
elaborated for a fatigue assessment.
Abstract: An experimental investigation was conducted to study the seismic behavior of slabcolumn
connections under vertical shear and cyclic lateral load. Test variables include gravity shear
ratio (V /V0 g ) and flexural reinforcement ratio (ρ ) of slab within an effective slab width between
lines that are one and one-half slab thickness ( c 3h 2 + ). The strength and ductility of the test
specimens were evaluated in accordance with gravity shear ratios and slab reinforcement ratios. The
shear strength of the test slabs was compared with the predictions by ACI 318-05.
Abstract: The impact testing is an efficient experimental method that enables the quantitative and
qualitative determination of the fatigue resistance of mono- and multilayer coatings deposited on
various substrates, which was not possible with the common testing methods previously available.
In this paper the experimental assessment of the fatigue resistance of coatings working under cyclic
loading conditions by means of the dynamic impact testing method is presented. The fatigue failure
mode, such cohesive or adhesive, of the investigated coatings is determined using scanning electron
and optical microscopy, as well as EDX analysis. Critical values of the stress components,
responsible for distinctive fatigue failure modes of the coating substrate system are obtained and the
fatigue limits of aluminide coatings are illustrated in simple diagrams containing the impact load
versus the number of successive impacts that the examined aluminide-P91 system can withstand.
Abstract: The constant-ductility seismic demand spectra can provide high-sight of seismic damage
mechanism of inelastic structures under the earthquake. And in the displacement-based seismic
design, the constant-ductility seismic demand spectra are very useful for the preliminary design of
new structures where the global displacement ductility capacity is known, which can provide the
required inelastic lateral strength of new structures from the required elastic lateral strength. An
in-depth investigation of damping effect on constant-ductility seismic demand spectra of inelastic
structures is presented in this paper. A statistical study is performed of inelastic response computed
for different damping ratio SDOF systems with different levels of lateral yielding strength required to
maintain the given displacement ductility when subjected to a large number earthquake accelerations.
It is concluded that the damping effect on constant-ductility seismic resistance spectra is rather
complex. It depends on not only site conditions but also the structural period. Finally, results from
non-linear regression analysis are presented that provide a simplified expression to be used to
approximately quantify the damping effect.
Abstract: Fattiigue and ttensiille properttiies of speciimens cutt from palllletts made from wastte pllasttiics by
usiing of newlly develloped recyclliing apparattus are presentted.. Testted matteriialls are pollypropyllene
fiillm,, pollypropyllene pelllletts,, pollyetthyllene,, pollyetthyllene-20wtt%flly ash composiitte and pollyetthyllene
-20wtt% callciium carbonatte composiitte.. Itt can be conclluded tthatt tthe newlly develloped recyclliing
apparattus make possiiblle tto proviide palllletts made from wastte pollypropyllene and pollyetthyllene wiitth
ullttiimatte ttensiille sttrengtths of more tthan niinetty percentt of tthose made from fresh pollypropyllene and
pollyetthyllene.. Itt has become cllear tthatt carefull ttreattmentt of composiitte process for wastte pllasttiics
enablle tto iimprove fattiigue sttrengtth of pollyetthyllene composiittes by sttrengttheniing tthe iintterface
bettween an addiittiive and base matteriiall..
Abstract: The optimization is the process of searching for the best results in a certain load case.
Complete definition of optimization includes three conditions, which are closely connected:
• optimization target, defined with object function,
• subject of optimization,
• optimization methods.
The object functions can be different process parameters such as costs, manufacturing time, costefficiency,
productivity etc. In designing of the structures such as a crane there is a tendency
particularly towards reducing the weight of steel structures with the same load-carrying capacity.
Thus the object function can be the volume, weight or mass of the structure.
In the paper we will devote ourselves to optimization of truss structures-gantry crane mean
girder by means of the FEM. This method has become indispensable in all areas of analyses of
structures in combination with mathematical modeling and mathematical methods of optimization
and is particularly of assistance to designers in conceiving the steel structures.
Abstract: In this paper the energy absorption of thin-walled aluminium tubes used as crash boxes in
the body structure of a vehicle has been optimized. In order to achieve this, various cross-sections
of extruded aluminium were chosen and their behaviour under dynamic impact loading was
investigated. The crash boxes were made from aluminium alloy 6060 temper T4. Finite element
software LS-DYNA in ANSYS was used for modelling. For each cross-section, the results of
dynamic crushing load versus crushing distance was obtained from the FE simulation and the
results were compared with the experimental and numerical work on a square crash box in the
literature. Parameters such as the crush force efficiency and the specific energy of various crash
boxes were compared with the relevant ones for the square crash box and the most efficient crash
box was recommended.
Abstract: In the last years there has been an increasing interest in the multi-scale mechanics of the
materials, i.e. in predicting the macroscopic constitutive response on the basis of the underlying
microstructure. At each level of structural hierarchy, one may model the material as a continuum,
and the representative volume element problem can be formulated in terms of standard equilibrium
and boundary conditions. The overall physical behaviour of these micro-heterogeneous materials
depends strongly on the shape, size, orientation, properties and spatial distribution of their
microconstituents. For prediction of the macroscopic behaviour of such materials the multi-scale
homogenization techniques were developed.
As an example of such investigation we develop the hierarchical material model of the chemical
vapour infiltrated carbon fiber composites (CFCs) with a unidirectional or random distribution of
fibers. The approach based on hierarchical structural modeling can be used to theoretically predict
the mechanical parameters of CFCs with different microstructure and to develop virtual materials
with prescribed mechanical properties.